Help! May Be Stranded DEF Fault
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Mountain Pass
Joined: Dec 2016
Posts: 225
Likes: 24
From: Columbus, Ohio
Help! May Be Stranded DEF Fault
Traveling 70E out of Higginsville, MO (east of St Louis) towing my 38 ft 5th wheel. Got a DEF warning DEF Fault speed will be limited to 50 mph in 50 miles. Found a Ford dealer, drove up & they are out of business. Great! On the forum people complain about this warning coming & going with no speed limitation. The owners manual says there is a miles countdown that follows this message which I didn’t get. Tempted to keep on going. Suggestions please?
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Mountain Pass
Joined: Dec 2016
Posts: 225
Likes: 24
From: Columbus, Ohio
Found a dealer, Joe Machens Ford in Columbia, Missouri. Chris Early, Service Advisor, met me at the door. Of course I was hard to miss pulling in with that trailer. But within a few minutes he has the tech looking at it & hopefully it’s just a bad sensor. While we were waiting another employee stopped by the lounge & offered a ride anywhere in the city. Great Service!
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Mountain Pass
Joined: Dec 2016
Posts: 225
Likes: 24
From: Columbus, Ohio
Tech & service advisor said no codes, seems to be running ok. They said that when I add DEF I should fill it completely up, if not the computer may not reset & think it’s still close to empty. I didn’t do that this morning, I just added the 2.5 gallon jug which on the gauge is about 3/4 full. Topping it off now & will reset the system so in a short time we should off!
More Turbo
Joined: Jun 2023
Posts: 609
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Tech & service advisor said no codes, seems to be running ok. They said that when I add DEF I should fill it completely up, if not the computer may not reset & think it’s still close to empty. I didn’t do that this morning, I just added the 2.5 gallon jug which on the gauge is about 3/4 full. Topping it off now & will reset the system so in a short time we should off!
Lead Driver
Joined: Nov 2005
Posts: 8,466
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Tech & service advisor said no codes, seems to be running ok. They said that when I add DEF I should fill it completely up, if not the computer may not reset & think it’s still close to empty. I didn’t do that this morning, I just added the 2.5 gallon jug which on the gauge is about 3/4 full. Topping it off now & will reset the system so in a short time we should off!
Now, when I start a trip, I do stop at a truck stop and top off at the pump, then do that jug add later in my trip.
And, the truck stop pump is really the only way to reliably top off, trying it with a jug will just get DEF spilled down the side of your truck and all over your shoes!
Also, since there were no codes, my bet is they will not find anything, and was probably just a momentary hiccup.
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Cargo Master
Joined: Apr 2018
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Traveling 70E out of Higginsville, MO (east of St Louis) towing my 38 ft 5th wheel. Got a DEF warning DEF Fault speed will be limited to 50 mph in 50 miles. Found a Ford dealer, drove up & they are out of business. Great! On the forum people complain about this warning coming & going with no speed limitation. The owners manual says there is a miles countdown that follows this message which I didn’t get. Tempted to keep on going. Suggestions please?
Both times or no check engine lights and everything appeared to be fine.
What had happened both times was the computer lost the value it's stored in the ECM. Both times Ford had to reflash the ECM. If they look through the ecm files, they have to look at the value of the quantity of the DEF tank.
The first time Ford was really puzzled, The second time was much easier with different dealer. Basically all they have to do is reflash the ECM.
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Lead Driver
Joined: Nov 2005
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That is another thing, the OP didn't give the 411 on his truck, no idea exactly what he has.
Cargo Master
Joined: Mar 2021
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Pretty sure mine goes down by the percent when it gets consumed and it goes up by the percent when you fill it up
